Fuel control system and associated method

ABSTRACT

A fuel control system for controlling the purging of alternate fuel in an internal combustion engine at shutdown includes: at least one valve device configured to deliver a fuel supply to the engine; a first fuel source configured to provide a primary fuel to the valve device; a second fuel source configured to provide an alternate fuel to the valve device; and a controller connected to the valve device and adapted to be connected to an ignition system. The controller is configured to control the valve device responsive to a status of one of the engine and the ignition system,

RELATED APPLICATIONS

This application claims priority from U.S. Provisional PatentApplication Ser. No. 60/744,857, filed Apr. 10, 2006, the disclosure ofwhich is hereby incorporated herein in its entirety.

FIELD OF THE INVENTION

The present invention relates to fuel systems for internal combustionengines and more particularly to fuel systems that provide both primaryfuel and alternate fuel to an internal combustion engine.

BACKGROUND OF THE INVENTION

For a variety of reasons, most of which relate to environmental andalternative energy pursuits, certain primary fuel engines, such asdiesel engines, can be made to accommodate alternate fuels, such asstraight vegetable oil (SVO), “biodiesel,” and other fuel oils(hereinafter “alternate fuels”). However, practical applications havedemonstrated that full-time use of these alternate fuels is notdesirable. For instance, at low temperatures the viscosity of some ofthese alternate fuels is not optimal for use in an engine designed torun on primary fuel. The alternate fuel should be heated up to atemperature that will allow it to easily pass through the fuel deliverysystem. If left in an idle engine to cool, the alternate fuel also has atendency to increase in viscosity and thus congeal or solidify insidethe fuel delivery components. Thus, the alternate fuel should not beused until it has reached an appropriate temperature and it should bepurged from the engine before shutting down. As a result, some of thesesystems typically run on diesel fuel during start-up and beforeshut-down, and rely on the consumer to manually switch to the alternatefuel source in between, i.e., when the alternate fuel is at a usableviscosity. For example, in an automobile that has been modified toinclude diesel and alternate fuel tanks, a driver can selectively togglebetween the two fuels during operation of the vehicle using a switchthat controls the flow of the two fuels.

Recently, some aftermarket automated control systems have been designed.These systems control the switching between a diesel fuel source and analternative fuel source based on the temperature of the alternate fuel.Typically, when the engine is cold, such as during engine start, theengine operates using primary fuel, and once a predetermined alternatefuel temperature or a certain vehicle speed is achieved, the engine isthen switched to the alternate fuel. If low temperature operationreoccurs, the engine is then switched back to primary fuel, and so on.

To automate this fuel selection process, various conventionalaftermarket control systems have been designed that acquire and monitoralternate fuel temperature by using various measurement devices, such astemperature sensors. However, these aftermarket systems do not addressthe condition whereby the engine is prematurely shut down during or ashort time after alternate fuel operation. Various concentrations ofalternate fuel will remain in fuel delivery components. If these fueldelivery components are subsequently allowed to cool, the alternate fuelwill congeal or solidify. Fuel flow therefore cannot be reestablishedfor start-up.

Therefore, an improved system and method of automatically purging aninternal combustion engine of alternate fuel are desired.

SUMMARY OF THE INVENTION

As a first aspect, embodiments of the invention are directed to a fuelcontrol system for controlling the purging of alternate fuel in aninternal combustion engine at shutdown. The system comprises: at leastone valve device configured to deliver a fuel supply to the engine; afirst fuel source configured to provide a primary fuel to the valvedevice; a second fuel source configured to provide an alternate fuel tothe valve device; and a controller connected to the valve device andadapted to be connected to an ignition system. The controller isconfigured to control the valve device responsive to a status of one ofthe engine and the ignition system.

In some embodiments, the controller is configured to detect a durationthat the engine operates, the duration ending with a signal from theignition system to cease operation of the engine. The controller isconfigured such that it signals the engine to continue to operate if theduration is less than a threshold time period.

As a second aspect, embodiments of the invention are directed to aninternal combustion engine assembly capable of operating on primary andalternate fuels, comprising: an internal combustion engine; a first fuelsource connected to the engine; a second fuel source connected to theengine; a fuel control unit connected with the first and second fuelsources for regulating fuel to the engine; an ignition system; and acontroller connected to the engine, the fuel control unit and theignition system. The controller is configured to control the fuelcontrol unit responsive to a status of one of the engine and theignition system.

As a third aspect, embodiments of the invention are directed to a methodof controlling the purging of alternate fuel in an internal combustionengine at shutdown. The method comprises the steps of: signaling aninternal combustion engine to cease operation, the signaling beingcarried out with an ignition system; detecting a status of one of theignition system and the internal combustion engine; and overriding thesignal from the ignition system responsive to the detected status suchthat the engine continues to operate in order to purge alternate fuel.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic diagram of an alternate fuel system for aninternal combustion engine according to the prior art.

FIG. 2 is a schematic diagram of an alternate fuel system with anignition system controller according to an embodiment of the presentinvention, the system being shown in a passive condition.

FIG. 3 is a schematic diagram of the alternate fuel system of FIG. 3,the system being shown in an active condition.

FIG. 4 is a schematic diagram of another alternate fuel system for aninternal combustion engine according to the prior art

FIG. 5 is a schematic diagram of an alternate fuel system with anignition system controller according to additional embodiments of thepresent invention, the system being shown in a passive condition.

FIG. 6 is a schematic diagram of the alternate fuel system of FIG. 5,the system being shown in an active condition.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The present invention now will be described more fully hereinafter withreference to the accompanying drawings, in which some, but not allembodiments of the invention are shown. Indeed, this invention may beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein; rather, these embodiments areprovided so that this disclosure will satisfy applicable legalrequirements. Like numbers refer to like elements throughout.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andwill not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an ” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof. As used herein the expression“and/or” includes any and all combinations of one or more of theassociated listed items.

In addition, spatially relative terms, such as “under”, “below”,“lower”, “over”, “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. It will beunderstood that the spatially relative terms are intended to encompassdifferent orientations of the device in use or operation in addition tothe orientation depicted in the figures. For example, if the device inthe figures is turned over, elements described as “under” or “beneath” sother elements or features would then be oriented “over” the otherelements or features. Thus, the exemplary term “under” can encompassboth an orientation of over and under. The device may be otherwiseoriented (rotated 90 degrees or at other orientations) and the spatiallyrelative descriptors used herein interpreted accordingly.

Well-known functions or constructions may not be described in detail forbrevity and/or clarity.

The present invention provides a fuel control system that can generallybe used as an inexpensive and easily adaptable solution for purgingalternate fuels whose tendency is to congeal or solidify if left withinfuel supply and delivery components. For purposes of this application,the term “selectively deliver,” and other forms thereof, is defined asproviding 100% primary fuel and 0% alternate fuel, or any mixture ofprimary and alternate fuel sufficient to prevent the tendency to congealor solidify if left within fuel supply and delivery components. Forpurposes of description within the accompanying drawings, fuel ispresumed delivered by pressure pump, suction pump or gravity, not shownfor simplicity, such that when restriction is removed within any fuelflow path, fuel will flow from source to engine. For purposes ofdescription within the accompanying drawings, although fuel presumeddelivered by pressure pump or suction pump often requires pressureregulation or excess flow bypass lines for implementation, such pressureregulation or excess flow bypass lines are similarly not shown forsimplicity.

Referring now to the drawings and, in particular, to FIG. 1, there isshown for purpose of reference and background a fuel control system 10in common use for providing primary and alternate fuel to an internalcombustion engine. The fuel used by engine 33 having fuel inlet 39 maybe primary fuel 21 contained in a first fuel source 22, an alternatefuel 23 contained in a second fuel source 24, or any combination of theprimary fuel 21 and the alternate fuel 23. The reference fuel controlsystem 10 depicted in FIG. 1 also includes a valve device 32 toselectively deliver primary fuel and alternate fuel, and a primary fueland alternate fuel selection control device 40 that asserts control ofvalve device 32 via electrical line 34. For purposes of thisapplication, the term “valve device” as generally depicted by device 32is defined as any device capable of controlling in any way the flow offuel or fuels. It should be noted that in various embodiments, a valvedevice many or may not include a valve. Also, for purposes of thisapplication, the term “primary fuel and alternate fuel selection controldevice” as generally depicted by device 40 is defined as any device, orsimple or complex system capable of issuing control or requesting theselection or mixing of fuel or fuels.

The reference fuel control system 10 depicted in FIG. 1 also includes anignition control device 41, typically, but not limited to, the primaryignition switch of the vehicle, wherein control device 41 asserts avoltage, current, or signal via electrical line 35 to permit engine 33to run, or alternately asserts a differing or absent voltage, current,or signal via line 35 to halt engine 33. For purposes of thisapplication, the term “ignition control device” as generally depicted bydevice 41 is defined as any device, or simple or complex system capableof controlling the run state of the engine by a variety of mechanisms,including but not limited to direct or indirect control upon fuel pumps,fuel injectors, glow plugs, valves and engine control modules. Also, forpurposes of description within this application, the term “ignition,”while not technically accurate in the context of a diesel engine, isnevertheless of common public use, parlance and understanding, andherein if and where used describes the ability to enable and disable therun state of engine by a variety of mechanisms, including but notlimited to direct or indirect control upon fuel pumps, fuel injectors,glow plugs, valves and engine control modules.

The reference fuel control system 10 depicted in FIG. 1 may also containheating element 30 for purpose of heating the alternate fuel 23contained in fuel source 24, and heating element 31 for purpose ofheating alternate fuel contained within fuel transmission line 26, withheat applied by such heating elements as present and distributed toliquefy and/or reduce the viscosity of alternate fuel 23 to effect itspassage though fuel transmission elements and component devices 26, 28,32, and 39 for consumption by engine 33.

The reference fuel control system 10 depicted in FIG. 1 possessesshortcomings and failure modes. Specifically, to effect immediate enginestart unconditionally upon user demand, the fuel transmission pathcomprising elements and component devices 26, 28, 32, and 39 betweenengine 33 and primary fuel 21 must within prior contain either primaryfuel 21 or a mixture of primary fuel 21 and alternate fuel 23 of suchratio not subject to congealment or solidification. As acounter-example, if vehicle engine 33 was being operated on alternatefuel 23 or a mixture of primary fuel 21 and alternate fuel 23 subject tocongealment or solidification at the time of engine 33 shut-off, fueltransmission element 28, valve device 32, and fuel inlet 39 upon coolingwill congeal or solidify within, effectively blocking fuel flow andthereby preventing engine restart. Additional heating elements such asthose depicted at 30 and 31 may be added and employed at fueltransmission elements and component devices 28, 32, and 39; however,such elements and component devices, and any fuel contained therein,will require time to heat in addition to the complexity added by theheating elements.

The present invention can address the problem of congealment andsolidification within fuel transmission and component devices to providefor immediate engine start or restart availability and vehicle usagewithout preconditions such as preheating, or dependencies upon userprocedures or conditions occurring at prior user engine shutdown, andcan do so such by introduction of an electronic controller, statusmonitoring, and control override mechanisms. Referring to the drawingsand, in particular, to FIG. 2, a fuel control system 11 is depicted in apassive state interposed within the basic primary fuel and alternatefuel selection control structure prior depicted in FIG. 1. The fuel usedby engine 33 having fuel inlet 28 may be primary fuel 21 contained in afirst fuel source 22, an alternate fuel 23 contained in a second fuelsource 24, or any combination of the primary fuel 21 and the alternatefuel 23. The fuel control system 11 depicted in FIG. 2 also includes avalve device 32 to selectively deliver primary fuel 21 and alternatefuel 23, and a primary fuel and alternate fuel selection control device40 that asserts control of valve device 28 through control overridemechanism 42 via a control signal on line 34. Furthermore, electroniccontroller 50 via a status signal on line 54 monitors the state ofcontrol device 40.

The fuel control system 11 depicted in FIG. 2 also includes an ignitioncontrol device 41, typically, but not limited to, the primary ignitionswitch of the vehicle, wherein control device 41 asserts a voltage,current, or signal through ignition override mechanism 43 and a controlsignal on line 35 to permit engine 33 to run, or alternately asserts adiffering or absent voltage, current, or signal through ignitionoverride mechanism 43 and line 35 to halt engine 33. Furthermore,electronic controller 50 via a status signal on line 55 monitors thestate of ignition control device 41. For purposes of this application,the term “ignition override mechanism” as generally depicted by device43 is defined any device, or simple or complex system capable ofusurping control over the run state of the engine by a variety ofmechanisms, including but not limited to gaining direct or indirectcontrol upon fuel pumps, fuel injectors, glow plugs, valves and enginecontrol modules.

The fuel control system 11 may also include an engine run sensor 58,whose purpose is to detect crankshaft rotation by direct or indirectmeans, and where such crankshaft rotation status is conveyed toelectronic controller 50 via a status signal on line 57.

The control override mechanism 42 is itself controlled by the controller50 via a control signal on line 52. While in the passive state asdepicted in FIG. 2, the control override mechanism 42 completely orsubstantially passes, or completely or substantially reproduces, thesignal as provided by the primary and alternate fuel control device 40,effectively passing or reproducing this signal to valve device 32 vialine 34.

The ignition override mechanism 43 is itself controlled by thecontroller 50 via a control signal on line 53. While in the passivestate as depicted in FIG. 2, the ignition override mechanism 43completely or substantially passes, or completely or substantiallyreproduces, the signal as provided by the vehicle ignition controldevice 41, effectively passing or reproducing this signal to the engine33 ignition control input via line 35.

While in the passive state as depicted in FIG. 2, if engine 33 isdetermined to be running via vehicle ignition control 41 and a statussignal on line 55, or alternately by or in conjunction with a separateengine run state status signal on line 57, at such time the status ofprimary fuel 21 and alternate fuel utilization is monitored asdetermined by the primary and alternate fuel control 40 via a statussignal on line 54 by electronic controller 50. If during this process ofmonitoring engine 33 via the signal on line 54 and the signals on line55 or 57 it is subsequently determined by electronic controller 50 thatthe signal on line 55 has transitioned as to indicate requested engine33 shutdown via ignition control 41, electronic controller 50 willexamine the history of primary fuel and alternate fuel utilization aswas monitored by a signal on line 54. If it is determined that primaryfuel 21 or a mixture of primary fuel 21 and alternate fuel 23 sufficientto preclude congealment or solidification resides within fueltransmission elements and component devices 28, 32, and 39, thenelectronic controller 50 will remain the passive state, therebypermitting engine shutdown. Otherwise, if it is determined thatalternate fuel 23 or a mixture of primary fuel 21 and alternate fuel 23insufficient to preclude congealment or solidification resides withinfuel transmission elements and component devices 28, 32, and 39, thenelectronic controller 50 will enter the active state, thereby precludingshutdown, unless an the emergency ignition shutoff signal is asserted online 56.

Referring to the drawings and, in particular, to FIG. 3, the fuelcontrol system 11 is depicted in the active state vs. the passive stateas previously shown in FIG. 2, and similarly interposed within the basicprimary fuel and alternate fuel selection control structure prior asdepicted in FIG. 1. All elements of FIG. 3 and the descriptions of suchelements therein are identical to those of FIG. 2 and apply, howeverwith notable exceptions being the state of control override mechanism 42and the state of ignition override mechanism 43.

Whereupon having transitioned from the passive state as depicted in FIG.2 to the active state as depicted in FIG. 3 for reason of determinationthat alternate fuel 23 or a mixture of primary fuel 21 and alternatefuel 23 insufficient to preclude congealment or solidification resideswithin fuel transmission elements and component devices 28, 32, and 39,electronic controller 50 asserts control signals on lines 52 and 53.Assertion of a control signal on line 52 causes control overridemechanism 42 to substantially disregard the state of the primaryalternate fuel control 40, and instead causes the control overridemechanism 42 to output a signal via line 34 to valve device 32 ofappropriate form or construct such that primary fuel 21 or a mixture ofprimary fuel 21 and alternate fuel 23 sufficient to preclude congealmentor solidification is selected by valve device 32. Furthermore, assertionof a control signal on line 53 causes control override mechanism 43 tosubstantially disregard the state of vehicle ignition control 41, andinstead causes the control override mechanism 42 to output a signal vialine 35 to engine 33 of appropriate from and construct such that engine33 remains in a running state.

While in the active state as depicted in FIG. 3, the assertion ofcontrol signals on lines 52 and 53, and in turn the assertion ofrespective override mechanisms 42 and 43, nominally continues for aperiod of time as determined by a threshold sufficient for primary fuel21 or a mixture of primary fuel 21 and alternate fuel 23 sufficient topreclude congealment or solidification to enter and purge substantiallyall of the alternate fuel from the fuel transmission elements andcomponent devices 28, 32, and 39. Upon expiration of said threshold,electronic controller 50 then ceases assertion of a control signal online 52, causing control override mechanism 42 to completely orsubstantially pass, or completely or substantially reproduce the signalas provided by the primary and alternate fuel control device 40,effectively passing or reproducing this signal to valve device 32 via acontrol signal on line 34. Furthermore, upon expiration of saidthreshold, electronic controller 50 then ceases assertion of a controlsignal on line 53, causing ignition override mechanism 43 to completelyor substantially pass, or to completely or substantially reproduce thesignal as provided by the vehicle ignition control device 41,effectively passing or reproducing this signal to the engine ignitioncontrol input via a control signal on line 35.

Upon expiration of said threshold and negation of assertion of controlsignals on lines 52 and 53, the fuel control system 11 as depicted inFIG. 3 in the active state transitions back to the passive state asdepicted in FIG. 2, whereupon it again waits for appropriate conditionsas described for and depicted within FIG. 2 before again transitioninginto the active state as described for FIG. 3, and so on.

If at any time during the active state as depicted in FIG. 3 theemergency ignition shutoff signal on line 56 is asserted by manual meansor by automated sensor including but not limited to vehicle fire,collision, or rollover, the fuel control system 11 may unconditionallynegate assertion of control signals on lines 52 and 53 and enter thepassive state.

If at any time during the active state as depicted in FIG. 3 electroniccontroller 50 senses repeated attempts or senses a pattern atypical ofnormal operation of vehicle ignition control 41 via a status signal online 55, the fuel control system 11 may unconditionally negate assertionof control signals on lines 52 and 53 and enter the passive state.

If at any time during the passive state as depicted in FIG. 2, theactive state as depicted in FIG. 3, the fuel control system 11 in partor total fails or loses electrical power, the system may be implementedsuch manner that it substantially emulates the passive state.

Referring now to the drawings and, in particular, to FIG. 4, there isshown for purpose of reference and background a fuel control system 12for providing primary and alternate fuel to an internal combustionengine. The fuel used by engine 33 having fuel inlets 36 and 37 may beprimary fuel 21 contained in a first fuel source 22, an alternate fuel23 contained in a second fuel source 24, or any combination of theprimary fuel 21 and the alternate fuel 23. The reference fuel controlsystem 12 depicted in FIG. 4 also includes a line 38 and alternate fuelselection control device 40 that asserts control via line 38. Forpurposes of this application, the term “primary fuel and alternate fuelselection control device” as generally depicted by device 40 is definedas any device, or simple or complex system capable of issuing control orrequesting the selection or mixing of fuel or fuels.

The reference fuel control system 12 depicted in FIG. 4 also includes anignition control device 41, typically, but not limited to, the primaryignition switch of the vehicle, wherein control device 41 asserts avoltage, current, or signal via line 35 to permit engine 33 to run, oralternately asserts a differing or absent voltage, current, or signalvia line 35 to halt engine 33.

The reference fuel control system 12 depicted in FIG. 4 may also containheating element 30 for purpose of heating the alternate fuel 23contained in fuel source 24, and heating element 31 for purpose ofheating alternate fuel contained within fuel transmission line 26, withheat applied by such heating elements as present and distributed toliquefy and/or reduce the viscosity of alternate fuel 23 to effect itspassage though fuel transmission elements and component devices 26 and36 for consumption by engine 33.

The reference fuel control system 12 depicted in FIG. 4 possessesshortcomings and failure modes. Specifically, to effect immediate enginestart unconditionally upon user demand, the fuel transmission pathcomprised of elements and component devices 26 and 36 between engine 33and primary fuel 21 must within prior contain either primary fuel 21 ora mixture of primary fuel 21 and alternate fuel 23 of such ratio notsubject to congealment or solidification. As a counter-example, ifvehicle engine 33 was being operated on alternate fuel 23 or a mixtureof primary fuel and alternate fuel subject to congealment orsolidification at the time of engine shut-off fuel transmission element26 and fuel inlet 36 upon cooling will congeal or solidify within,effectively blocking fuel flow and thereby preventing engine restart.Additional heating elements such as those depicted at 30 and 31 may beadded and employed at fuel transmission elements and component devices;however, such elements and component devices, and any fuel containedtherein, will require time to heat in addition to the complexity addedby said heating elements.

A different embodiment of the present invention addresses the problem ofcongealment and solidification to provide for immediate engine start orrestart availability and vehicle usage without preconditions such aspreheating, or dependencies upon user procedures or conditions occurringat prior user engine shutdown, and does such by introduction of anelectronic controller, status monitoring, and control overridemechanisms. Referring to the drawings and, in particular, to FIG. 5, afuel control system 13 is depicted in a passive state interposed withinthe basic primary fuel and alternate fuel selection control structureprior depicted in FIG. 4. The fuel used by engine 33 having fuel inlets36 and 37 may be primary fuel 21 contained in a first fuel source 22, analternate fuel 23 contained in a second fuel source 24, or anycombination of the primary fuel 21 and the alternate fuel 23. The fuelcontrol system 13 depicted in FIG. 5 also includes engine 33 capable ofaccepting primary fuel 21 and alternate fuel 23, and a primary fuel andalternate fuel selection control device 40 that asserts control ofengine 33 fuel selection through control override mechanism 42 viacontrol signals on line 38. Furthermore, electronic controller 50 via astatus signal on line 54 monitors the state of control device 40.

The fuel control system 13 depicted in FIG. 5 also includes a valvedevice 29 to selectively deliver primary fuel 21 and alternate fuel 23through alternate fuel transmission line 27 and engine inlet 36, and aprimary fuel 21 and alternate fuel selection control signal line 51 thatconnects valve device 29 and electronic controller 50.

The fuel control system 13 depicted in FIG. 5 also includes an ignitioncontrol device 41, typically, but not limited to, the primary ignitionswitch of the vehicle, wherein control device 41 asserts a voltage,current, or signal through ignition override mechanism 43 and line 35 topermit engine 33 to run, or alternately asserts a differing or absentvoltage, current, or signal through ignition override mechanism 43 andline 35 to halt engine 33. Furthermore, electronic controller 50 via astatus signal on line 55 monitors the state of ignition control device41.

The fuel control system 13 may also include an engine run sensor 58,whose purpose is to detect crankshaft rotation by direct or indirectmeans, and where such crankshaft rotation status is conveyed toelectronic controller 50 via a status signal on line 57.

Valve device 29 is itself controlled by control signals on line 51.While in the passive state as depicted in FIG. 5, the valve device 29completely or substantially directs alternate fuel 23 from fueltransmission line 26 to fuel transmission line 27.

The control override mechanism 42 is itself controlled by controlsignals on line 52. While in the passive state as depicted in FIG. 5,the control override mechanism 42 completely or substantially passes, orcompletely or substantially reproduces, the signal as provided by theprimary and alternate fuel control device 40, effectively passing orreproducing this signal to engine 33 to effect fuel selection viacontrol signals on line 38.

The ignition override mechanism 43 is itself controlled by controlsignals on line 53. While in the passive state as depicted in FIG. 5,the ignition override mechanism 43 completely or substantially passes,or completely or substantially reproduces, the signal as provided by thevehicle ignition control device 41, effectively passing or reproducingthis signal to the engine 33 ignition control input via control signalson line 35.

While in the passive state as depicted in FIG. 5, if engine 33 isdetermined to be running via vehicle ignition control 41 and statussignals on line 55, or alternately by or in conjunction with separateengine run state status signals on line 57, at such time the status ofprimary fuel 21 and alternate fuel 23 utilization is monitored asdetermined by the primary and alternate fuel control 40 via a statussignal on line 54 by electronic controller 50. If during this process ofmonitoring engine 33 via a signal on line 54 and signals on line 55 or57 it is subsequently determined by electronic controller 50 that thesignal on line 55 has transitioned as to indicate requested engineshutdown via ignition control 41, electronic controller 50 will examinethe history of primary fuel and alternate fuel utilization as wasmonitored via line 54. If it is determined that alternate fuel 23 wasnot utilized within fuel transmission elements and component devices 27,29, and 36, then electronic controller 50 will remain the passive state,thereby permitting engine shutdown. Otherwise, if it is determined thatalternate fuel 23 was utilized within fuel transmission elements andcomponent devices 27, 29, and 36, then electronic controller 50 willenter the active state, thereby precluding shutdown, unless theemergency ignition shutoff signal is asserted via line 56.

Referring to the drawings and, in particular, to FIG. 6, the fuelcontrol system 13 is depicted in the active state vs. the passive stateas previously shown in FIG. 5, and similarly interposed within the basicprimary fuel and alternate fuel selection control structure prior asdepicted in FIG. 4. All elements of FIG. 6 and the descriptions of suchelements therein are identical to those of FIG. 5 and apply, howeverwith notable exceptions being the state of control override mechanism 42as controlled by a control signal on line 52, and the state of ignitionoverride mechanism 43 as controlled by a control signal on line 53.

Whereupon having transitioned from the passive state as depicted in FIG.5 to in the active state as depicted in FIG. 6 for reason ofdetermination that alternate fuel 23 resides within fuel transmissionelements and component devices 27, 29, and 36, electronic controller 50asserts control signals on lines 51, 52 and 53. Assertion of a controlsignal on line 51 causes valve 29 to transition such that any fuelsubsequently consumed by engine 33 via inlet 36 be comprised of primaryfuel 21 or a mixture of primary fuel 21 and secondary fuel 23 of ratiosufficient to preclude congealment or solidification. Assertion of acontrol signal on line 52 causes control override mechanism 42 tosubstantially disregard the state of the primary alternate fuel control40, and instead causes the control override mechanism 42 to output asignal via line 38 to engine 33 of appropriate form or construct suchthat alternate fuel inlet 36 is selected for fuel utilization, or acombination of alternate fuel inlet 36 and primary fuel inlet 37sufficient to also induce flow at alternate fuel inlet 36 is selected.Furthermore, assertion of a control signal on line 53 causes controloverride mechanism 43 to substantially disregard the state of vehicleignition control 41, and instead causes the control override mechanism42 to output a signal via line 35 to engine 33 of appropriate from andconstruct such that engine 33 remains in a running state.

While in the active state as depicted in FIG. 6, assertion of controlsignals on lines 51, 52 and 53, and the respective transitioning ofvalve device 29 and assertion of override mechanisms 42 and 43 nominallycontinues for a period of time as determined by a threshold sufficientfor primary fuel 21 or a mixture of primary fuel 21 and alternate fuel23 sufficient to preclude congealment or solidification to enter andpurge fuel transmission elements and component devices 27, 29, and 36.Upon expiration of said threshold, electronic controller 50 then ceasesassertion of a control signal on line 51 causing valve device 29 tocompletely or substantially direct alternate fuel 23 from fueltransmission line 26 to fuel transmission line 27. Also upon expirationof said threshold, electronic controller 50 then ceases assertion of acontrol signal on line 52, causing control override mechanism 42 tocompletely or substantially pass, or completely or substantiallyreproduce, the signal as provided by the primary and alternate fuelcontrol device 40, effectively passing or reproducing this signal engine33 via a control signal on line 38. Furthermore, upon expiration of saidthreshold, electronic controller 50 then ceases assertion of a controlsignal on line 53, causing ignition override mechanism 43 to completelyor substantially pass, or completely or substantially reproduce, thesignal as provided by the vehicle ignition control device 41,effectively passing or reproducing this signal to the engine 33 ignitioncontrol input via a control signal on line 35.

Upon expiration of-said threshold and negation of assertion of controlsignals on lines 51, 52 and 53, the fuel control system 13 as depictedin FIG. 6 in the active state transitions back to the passive state asdepicted in FIG. 5, whereupon it again waits for appropriate conditionsas described for and depicted within FIG. 5 before again transitioninginto the active state as described for FIG. 6, and so on.

If at any time during the active state as depicted in FIG. 6 theemergency ignition shutoff signal on line 56 is asserted by manual meansor by automated sensors including but not limited to vehicle fire,collision, or rollover, the fuel control system 13 may unconditionallynegate assertion of control signals on lines 51, 52 and 53 and enter thepassive state.

If at any time during the active state as depicted in FIG. 6 electroniccontroller 50 senses repeated attempts or senses a pattern atypical ofnormal operation of vehicle ignition control 41 via a status signal online 55, the fuel control system 13 may unconditionally negate assertionof control signals on lines 51, 52 and 53 and enter the passive state.

If at any time during the passive state as depicted in FIG. 5 or theactive state as depicted in FIG. 6, the fuel control system 13 in partor total fails or loses electrical power, the system may be implementedsuch manner that it substantially emulates the passive state.

Many modifications and other embodiments of the inventions set forthherein will come to mind to one skilled in the art to which thisinvention pertains having the benefit of the teachings presented in theforegoing descriptions and associated drawings. Therefore, it is to beunderstood that the invention is not to be limited to the specificembodiments disclosed and that modifications and other embodiments areintended to be included within the scope of the appended claims.Although specific terms are employed herein, they are used in a genericand descriptive sense only and not for purposes of limitation.

1. A fuel control system for controlling the purging of alternate fuelin an internal combustion engine at shutdown, comprising: at least onevalve device configured to deliver a fuel supply to the engine; a firstfuel source configured to provide a primary fuel to the valve device; asecond fuel source configured to provide an alternate fuel to the valvedevice; a controller connected to the valve device and adapted to beconnected to an ignition system, the controller being configured tocontrol the valve device responsive to a status of one of the engine andthe ignition system.
 2. The fuel control system defined in claim 1,wherein the controller is configured to detect a duration that theengine operates, the duration ending with a signal from the ignitionsystem to cease operation of the engine, and wherein the controller isconfigured such that it signals the engine to continue to operate if theduration is less than a threshold time period.
 3. The fuel controlsystem defined in claim 2, wherein the controller includes a sensorconfigured to sense engine operation.
 4. The fuel control system definedin claim 2, further comprising fuel lines between the second fuel sourceand the engine, and wherein the controller signals the engine tocontinue to operate for a time sufficient to purge substantially all ofthe alternate fuel from the fuel lines.
 5. The fuel control systemdefined in claim 1, further comprising a sensor that is configured tosense a ratio of alternate fuel to primary fuel, and wherein thecontroller is configured to signal the engine to continue to operatedespite a signal from the ignition system to cease operation if theratio of alternate fuel to primary fuel is above a threshold value. 6.The fuel control system defined in claim 5, further comprising fuellines between the second fuel source and the engine, and wherein thecontroller signals the engine to continue to operate for a timesufficient to purge substantially all of the alternate fuel from fuellines.
 7. The fuel control system defined in claim 1, wherein thecontroller is further configured such that receiving multiple cessationsignals from the ignition system allows the engine to cease operation.8. The fuel control system defined in claim 1, wherein the controller isfurther configured such that receiving an emergency ignition shutoffsignal from an emergency stop signal source allows the system to ceaseoperation.
 9. An internal combustion engine assembly capable ofoperating on primary and alternate fuels, comprising: an internalcombustion engine; a first fuel source connected to the engine; a secondfuel source connected to the engine; a fuel control unit connected withthe first and second fuel sources for regulating fuel to the engine; anignition system; and a controller connected to the engine, the fuelcontrol unit and the ignition system, the controller being configured tocontrol the fuel control unit responsive to a status of one of theengine and the ignition system.
 10. The engine assembly defined in claim9, wherein the controller is configured to detect a duration that theengine operates, the duration ending with a signal from the ignitionsystem to cease operation of the engine, and wherein the controller isconfigured such that it signals the engine to continue to operate if theduration is less than a threshold time period.
 11. The engine assemblydefined in claim 97 wherein the controller includes a sensor configuredto sense engine operation.
 12. The engine assembly defined in claim 9,wherein the controller signals the engine to continue to operate for atime sufficient to purge substantially all of the alternate fuel fromthe fuel lines connecting the second source to the engine.
 13. Theengine assembly defined in claim 9, further comprising a sensor that isconfigured to sense a ratio of alternate fuel to primary fuel, andwherein the controller is configured to signal the engine to continue tooperate despite a signal from the ignition system to cease operation ifthe ratio of alternate fuel to primary fuel is above a threshold value.14. The engine assembly defined in claim 13, wherein the controllersignals the engine to continue to operate for a time sufficient to purgesubstantially all of the alternate fuel from fuel lines connecting thesecond fuel source to the engine.
 15. The engine assembly defined inclaim 9, wherein the controller is further configured such thatreceiving multiple cessation signals from the ignition system allows theengine to cease operation.
 16. The engine assembly defined in claim 9,wherein the controller is further configured such that receiving anemergency ignition shutoff signal from an emergency stop signal sourceallows the system to cease operation.
 17. The engine assembly defined inclaim 9, wherein the fuel control device includes a valve.
 18. A methodof controlling the purging of alternate fuel in an internal combustionengine at shutdown, comprising: signaling an internal combustion engineto cease operation, the signaling being carried out with an ignitionsystem; detecting a status of one of the ignition system and theinternal combustion engine; and overriding the signal from the ignitionsystem responsive to the detected status such that the engine continuesto operate in order to purge alternate fuel.
 19. The method defined inclaim 18, wherein the detecting step comprises detecting the durationthat the engine has been operating, and wherein the overriding stepcomprises overriding the ignition signal if the detected duration isless than a predetermined threshold.
 20. The method defined in claim 18,wherein the detecting step comprises detecting a ratio of alternate fuelto primary fuel in the engine, and the overriding step comprisesoverriding the signal from the ignition system if the ratio is higherthan a predetermined value.
 21. The method defined in claim 18, furthercomprising the steps of detecting multiple signals from the ignitionsystem, and ignoring the overriding step such that the engine ceasesoperation.